Fig. 2. Correction of initial velocity conditions for calculation of the guinea fowl's COM path. Initial velocity conditions derived using standard methods result in a path that diverges considerably from kinematic observation. The calculated vertical position (A, broken red line) and the observed kinematic estimates (black dots) relate to the left axes in A and B, and show a discrepancy represented as the squared difference at each point (grey vertical bars, right axes in A and B). The sum of the squared differences through the step period (SSD, inset in A and B) is used as a statistic for selecting the V_i,v that minimizes the divergence between the two vertical paths. The V_i values resulting in the closest path match for the vertical (B, solid blue line) and horizontal components (not displayed, but identical principles), are then used as the integration constants in the calculation of instantaneous velocities from the ground reaction force data (Eqn 5, 6).